If you are after something equivalent to window.prompt then there isn't anything built in to Espruino at the moment, however you might find this forum post does what you want:
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
If you are after something equivalent to
window.prompt
then there isn't anything built in to Espruino at the moment, however you might find this forum post does what you want:http://forum.espruino.com/conversations/329366/